Fix linker regression for Visual Studio
Fix linker regression for Visual Studio

Commit cb77067f554683fcf972cff0b497e9c4bfd3d877 changed the declaration of
null_script. An additional TESS_API is needed to satisfy the VS linker.

Signed-off-by: Stefan Weil <8d4c780fcfdc41841e5070f4c43da8958ba6aec0@weilnetz.de>

UB-Mannheim/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,jbarlow83/tesseract,stweil/tesseract,tesseract-ocr/tesseract,amitdo/tesseract,stweil/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,stweil/tesseract,tesseract-ocr/tesseract,amitdo/tesseract,UB-Mannheim/tesseract,amitdo/tesseract,tesseract-ocr/tesseract,tesseract-ocr/tesseract,stweil/tesseract,stweil/tesseract,jbarlow83/tesseract,jbarlow83/tesseract,jbarlow83/tesseract,UB-Mannheim/tesseract,jbarlow83/tesseract